I've been following other posts here on similar issues of rough running, and think there is some great feedback/responses here. My issue seems unique (at least in posts I've found) since the engine runs strong for a substantial period - a couple of hours at least - and then starts to run rough with misfiring, rough running, and even stalling on occasion. I can always restart the engine after stalling, and sometimes it runs great after restarting, but not always. And the symptoms always come back, eventually. This issue has persisted for years, and I have not been able to resolve it regardless of any measure I take.
Some background: Late model A4, completely rebuilt in 2006 with most upgrades from Moyer (and some from Indigo) - FWC, Ignitor EI, Facet Electric fuel pump, crankcase ventilator, and this year new wires, plugs, rotor and EI cap. Also added a new coil with ballast resistor from Indigo. I have zero overheating issues - the engine runs consistently at 180 degrees. I have cleaned the carb, but really found no issue there. During the latest episode this past weekend, I suspected the flame arrestor (the circular one Moyer used to sell but don't see it available currently) may have become too clogged with crankcase vapor so I 'loosened' it thinking air intake was the issue (even tried running the engine with the compartment cover off), but still no improvement. I use ethanol free gas, with appropriate MMO added.
Some things I have not done (and now that I'm home and three hours away from the boat I realize I should have done): Replaced Racor Fuel filter (2 years old now), drained water from racer filter, replaced inline fuel filter between fuel pump and carb.
My gut tells me it is an electrical issue, but what is causing it eludes me. It also feels like it could be sticking valves (but why stick after 2 hours of running fine?) or water in the fuel (but why would water get introduced after 2 hours of running fine?). Why would it run fine for hours, well beyond the engine/compartment coming up to temp, and then run badly? I also feel it could be a temp issue, where some electrical component becomes compromised after enough exposure to a 180 degree engine. Could a compromised wire/connection/component run fine for a while, but become compromised after a couple hours exposure to an engine running at 180 (that's why I replaced the coil, and am tempted to replace the EI too, but already too much $$$)? I'm at a loss, and would appreciate any feedback.
Thanks in advance,
John
Some background: Late model A4, completely rebuilt in 2006 with most upgrades from Moyer (and some from Indigo) - FWC, Ignitor EI, Facet Electric fuel pump, crankcase ventilator, and this year new wires, plugs, rotor and EI cap. Also added a new coil with ballast resistor from Indigo. I have zero overheating issues - the engine runs consistently at 180 degrees. I have cleaned the carb, but really found no issue there. During the latest episode this past weekend, I suspected the flame arrestor (the circular one Moyer used to sell but don't see it available currently) may have become too clogged with crankcase vapor so I 'loosened' it thinking air intake was the issue (even tried running the engine with the compartment cover off), but still no improvement. I use ethanol free gas, with appropriate MMO added.
Some things I have not done (and now that I'm home and three hours away from the boat I realize I should have done): Replaced Racor Fuel filter (2 years old now), drained water from racer filter, replaced inline fuel filter between fuel pump and carb.
My gut tells me it is an electrical issue, but what is causing it eludes me. It also feels like it could be sticking valves (but why stick after 2 hours of running fine?) or water in the fuel (but why would water get introduced after 2 hours of running fine?). Why would it run fine for hours, well beyond the engine/compartment coming up to temp, and then run badly? I also feel it could be a temp issue, where some electrical component becomes compromised after enough exposure to a 180 degree engine. Could a compromised wire/connection/component run fine for a while, but become compromised after a couple hours exposure to an engine running at 180 (that's why I replaced the coil, and am tempted to replace the EI too, but already too much $$$)? I'm at a loss, and would appreciate any feedback.
Thanks in advance,
John
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